I. Field of the Invention
This invention pertains to animal isolators. More particularly, this invention pertains to an air filtering cabinet with an associated animal rack. The cabinet is used to filter air which is drawn through the animal rack or to filter air prior to its being blown through an animal rack, or both.
II. Description of the Prior Art
Animal isolators (which may alternatively be called animal stations) are widely used in connection with the care, feeding and experimentation with laboratory animals such as rats, rabbits and the like. The purpose of such stations is to protect animals and laboratory personnel from microorganisms which might produce disease or effect results of experimentation. It is also desirable to minimize cross contamination of germs from one animal to another.
An example of an animal station is shown in U.S. Pat. No. 4,023,529 to Landy dated May 17, 1977 (the Landy patent). Such an apparatus is also shown and described in a brochure entitled "LAMINER AIR FOR ANIMAL CARE" of the Germ-Free Laboratories, Inc. which describes the structure and operation of their products Single-Flow Animal Station and Double-Flow Animal Station (having apparent product designation numbers of SFAS-30 and DFAS-60, respectively). As shown in both of these publications, the animal station includes a cabinet having a blower and a filter covering openings form through the cabinet walls. In the Double-Flow Animal Station as shown most clearly in the Germ-Free Laboratories, Inc. brochure, the cabinet includes front and back walls having openings. Covering each of the front and back wall openings are high efficiency particulate air filters (known generally as HEPA filters). In the embodiment shown in the third page of the brochure, the Double-Flow Animal Station is operated at a positive pressure. Namely, the interior of the cabinet is at a higher pressure than ambient air. As a result, air is drawn through a prefilter (designated at numeral 2) through the blower (1) and out through the HEPA filters (3). Animal cages may be positioned exterior of the cabinet on racks positioned adjacent both the front and back walls. This arrangement is shown on the second page of the brochure.
The arrangement shown in the third page of the Germ-Free Laboratories, Inc. brochure, and described above, provides for clean air flow to the animals disposed within the cages adjacent the cabinet walls. Such an arrangement would be desirable where the protection of the animals is the primary concern. However, in laboratory applications, it is commonly desirable to provide for protection of the environment. Namely, with the embodiment shown on the third page of the Germ-Free Laboratories, Inc. brochure, any dust, dander and germs from the animals will be blown in the atmosphere and may be inhaled by laboratory personnel.
Where it is desirable to prevent germs and dander from contaminating the laboratory air, air is drawn through the animal cages and then through the filters. This reverse flow may be referred to as a negative pressure system where the pressure within the chamber is less than the pressure in ambient air. Such an arrangement is shown on the last page of the brochure of Germ-Free Laboratories, Inc.
From time to time, it may be desirable to modify a clean animal station so that it may cause air to flow from a HEPA filter to the animals (positive air flow) or from the room pass the animals to the HEPA filter (negative pressure system). The former is for the protection of the animals and the latter is for the protection of personnel in the lab. With the prior art apparatus, disassembly and reassembly of the filter arrangements may be required. For example, a comparison of the positive and negative pressure systems in the Germ-Free Laboratories, Inc. brochure shows different placement of a prefilter in the two systems. Further, once the direction of air flow through the HEPA filter has been established and the HEPA filter has been used, the system cannot be reversed since reversal of air flow will blow contaminants off of the filter and may lead to injury to either animals or humans.